The present invention relates generally to transformers and, more particularly, to transformer windings and processes for producing a modular section foil coil for cast resin windings.
Transformers are used extensively in electrical and electronic applications. Transformers are useful to step voltages up or down, to couple signal energy from one stage to another, and for impedance matching. Transformers are also useful for sensing current and powering electronic trip units for circuit interrupters such as circuit breakers and other electrical distribution devices. Generally, the transformer is used to transfer electric energy from one circuit to another circuit using magnetic induction.
A transformer includes two or more multi-turned coils of wire placed in close proximity to cause a magnetic field of one coil to link to a magnetic field of the other coil. Most transformers have a primary winding and a secondary winding. By varying the number of turns contained in the primary winding with respect to the number of turns contained in the secondary winding, the output voltage of the transformer can be easily increased or decreased.
The magnetic field generated by the current in the primary coil or winding may be greatly concentrated by providing a core of magnetic material on which the primary and secondary coils are wound. This increases the inductance of the primary and secondary coils so that a smaller number of turns may be used. A closed core having a continuous magnetic path also ensures that practically all of the magnetic field established by the current in the primary coil will be induced in the secondary coil.
When an alternating voltage is applied to the primary winding, an alternating current flows, limited in value by the inductance of the winding. This magnetizing current produces an alternating magnetomotive force which creates an alternating magnetic flux. The flux is constrained within the magnetic core of the transformer and induces voltage in the linked secondary winding, which, if it is connected to an electrical load, produces an alternating current. This secondary load current then produces its own magnetomotive force and creates a further alternating flux which links back with the primary winding. A load current then flows in the primary winding of sufficient magnitude to balance the magnetomotive force produced by the secondary load current. Thus, the primary winding carries both magnetizing and load current, the secondary winding carries load current, and the magnetic core carries only the flux produced by the magnetizing current.
Disk-type high voltage windings are quite popular in vacuum/pressure impregnated open wound transformers. The disk conductors are supported within cut combs which are symmetrically placed approximately 4xe2x80x3 apart around the circumference of the winding mandrel. Each winding disk is electrically connected to an adjacent winding disk using start-to-finish connections. Disk windings require at least xc2xdxe2x80x3 to xc2xexe2x80x3 disk-to-disk space for mechanical reasons for routing the disk-to-disk connections. Generally, the number of disks used in a winding is kept to a minimum in order to minimize the labor cost of the winding.
The use of disk type high voltage cast windings using foil-type conductors is becoming popular in dry type transformers. This type of winding configuration is cost efficient because it is easily produced on an automated winding machine. Typically, disks wound with strip conductors have not been utilized in dry type vacuum/pressure impregnated (VPI) open-wound windings. When disk type windings are used in VPI open-wound designs, they are usually configured with a plurality of disks which are wound using a rectangular cross-section conductor. These windings typically comprise a rectangular conductive element.
The present invention is directed to a transformer comprising modular sections, each modular section comprising a disk winding. The transformer comprises a winding structure including high voltage modular sections.
Each modular section is positioned about a central axis. The modular sections generally comprise a support and a winding. The support is positioned about the central axis and the winding comprises a conductive element located about the support. The winding may be wound about the support, or alternatively, the winding can be wound separately prior to being positioned about the support and encapsulated with epoxy.
The support comprises an inner supporting ring, an outer supporting ring, and spacer supports. The inner supporting ring is radially spaced from the outer supporting ring by the spacer supports. Radial air ducts are formed between the space between the inner supporting ring and the outer supporting ring.
The support comprises an insulating material, for example the dielectric material used to vacuum pressure impregnate, encapsulate, and seal the coils, cardboard, or any other rigid or semirigid insulting material. The support can be implemented during winding of the conductive element or added later and primarily formed by the baked and hardened dielectric material.
The winding comprises an inner segment and an outer segment. The inner segment is located about the inner supporting ring. Similarly, the outer segment is located about the outer supporting ring. The winding is terminated at an electrical coupling. The electrical coupling removably connects one modular section to another modular section.
The electrical coupling is generally a plug-in type connector. The electrical coupling is located on an upper surface of the modular section. Another electrical coupling is located on a lower surface. The couplings are adapted to be operatively connectable with one another when the upper surface of one modular section is placed adjacent the lower surface of another modular section.
Each modular section further comprises a means for properly aligning adjacent modular sections. When in proper alignment, the modular sections are axially aligned along the central axis. Each modular section includes a key member that extends outwardly from the upper surface. The lower surface of the modular section includes a corresponding key receiver which is adapted to receive the key member to properly align the modular sections.
Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings.